Strong long-range perpendicular exchange bias across a spacer layer

Abstract

The perpendicular magnetic anisotropy (PMA) and perpendicular exchange bias (PEB) have been investigated in a CoPt/spacer/FeMn heterostructure by inserting Ta and Pt as spacer layers, respectively. First, we show that strong PMA can be obtained in (111)-oriented A1-CoPt single layer and CoPt/FeMn bilayer films on MgO (111) substrates. Then we demonstrate that the Ta and Pt spacer layers have largely different effects on the PMA and PEB of the CoPt/spacer/FeMn films. By increasing the thickness of the Ta spacer layer to 1 nm, the PMA and PEB drastically decrease. While, in the case of Pt, the PMA and PEB increase first, then slightly decrease. When the Pt spacer layer is 1 nm, a value of 85 Oe of the long-range PEB still can be obtained. The possible mechanisms were discussed to explain the different trends of PMA and PEB. Since Ta and Pt are the generally used materials in the spintronics, our study provides a piece of information for the control of the magnetic anisotropy and exchange bias in the current-induced magnetization switching of ferromagnet without external magnetic field.